#include "zgl.h"

/* fill triangle profile */
/* #define PROFILE */

#define CLIP_XMIN (1 << 0)
#define CLIP_XMAX (1 << 1)
#define CLIP_YMIN (1 << 2)
#define CLIP_YMAX (1 << 3)
#define CLIP_ZMIN (1 << 4)
#define CLIP_ZMAX (1 << 5)

void gl_transform_to_viewport(GLContext* c, GLVertex* v) {
  float winv;

  /* coordinates */
  winv = 1.0 / v->pc.W;
  v->zp.x = (int)(v->pc.X * winv * c->viewport.scale.X + c->viewport.trans.X);
  v->zp.y = (int)(v->pc.Y * winv * c->viewport.scale.Y + c->viewport.trans.Y);
  v->zp.z = (int)(v->pc.Z * winv * c->viewport.scale.Z + c->viewport.trans.Z);
  /* color */
  if (c->lighting_enabled) {
    v->zp.r = (int)(v->color.v[0] * (ZB_POINT_RED_MAX - ZB_POINT_RED_MIN) + ZB_POINT_RED_MIN);
    v->zp.g = (int)(v->color.v[1] * (ZB_POINT_GREEN_MAX - ZB_POINT_GREEN_MIN) + ZB_POINT_GREEN_MIN);
    v->zp.b = (int)(v->color.v[2] * (ZB_POINT_BLUE_MAX - ZB_POINT_BLUE_MIN) + ZB_POINT_BLUE_MIN);
  } else {
    /* no need to convert to integer if no lighting : take current color */
    v->zp.r = c->longcurrent_color[0];
    v->zp.g = c->longcurrent_color[1];
    v->zp.b = c->longcurrent_color[2];
  }

  /* texture */

  if (c->texture_2d_enabled) {
    v->zp.s = (int)(v->tex_coord.X * (ZB_POINT_S_MAX - ZB_POINT_S_MIN) + ZB_POINT_S_MIN);
    v->zp.t = (int)(v->tex_coord.Y * (ZB_POINT_T_MAX - ZB_POINT_T_MIN) + ZB_POINT_T_MIN);
  }
}

static void gl_add_select1(GLContext* c, int z1, int z2, int z3) {
  unsigned int min, max;
  min = max = z1;
  if (z2 < min) min = z2;
  if (z3 < min) min = z3;
  if (z2 > max) max = z2;
  if (z3 > max) max = z3;

  gl_add_select(c, 0xffffffff - min, 0xffffffff - max);
}

/* point */

void gl_draw_point(GLContext* c, GLVertex* p0) {
  if (p0->clip_code == 0) {
    if (c->render_mode == GL_SELECT) {
      gl_add_select(c, p0->zp.z, p0->zp.z);
    } else {
      ZB_plot(c->zb, &p0->zp);
    }
  }
}

/* line */

static inline void interpolate(GLVertex* q, GLVertex* p0, GLVertex* p1, float t) {
  q->pc.X = p0->pc.X + (p1->pc.X - p0->pc.X) * t;
  q->pc.Y = p0->pc.Y + (p1->pc.Y - p0->pc.Y) * t;
  q->pc.Z = p0->pc.Z + (p1->pc.Z - p0->pc.Z) * t;
  q->pc.W = p0->pc.W + (p1->pc.W - p0->pc.W) * t;

  q->color.v[0] = p0->color.v[0] + (p1->color.v[0] - p0->color.v[0]) * t;
  q->color.v[1] = p0->color.v[1] + (p1->color.v[1] - p0->color.v[1]) * t;
  q->color.v[2] = p0->color.v[2] + (p1->color.v[2] - p0->color.v[2]) * t;
}

/*
 * Line Clipping 
 */

/* Line Clipping algorithm from 'Computer Graphics', Principles and
   Practice */
static inline int ClipLine1(float denom, float num, float* tmin, float* tmax) {
  float t;

  if (denom > 0) {
    t = num / denom;
    if (t > *tmax) return 0;
    if (t > *tmin) *tmin = t;
  } else if (denom < 0) {
    t = num / denom;
    if (t < *tmin) return 0;
    if (t < *tmax) *tmax = t;
  } else if (num > 0)
    return 0;
  return 1;
}

void gl_draw_line(GLContext* c, GLVertex* p1, GLVertex* p2) {
  float dx, dy, dz, dw, x1, y1, z1, w1;
  float tmin, tmax;
  GLVertex q1, q2;
  int cc1, cc2;

  cc1 = p1->clip_code;
  cc2 = p2->clip_code;

  if ((cc1 | cc2) == 0) {
    if (c->render_mode == GL_SELECT) {
      gl_add_select1(c, p1->zp.z, p2->zp.z, p2->zp.z);
    } else {
      if (c->depth_test)
        ZB_line_z(c->zb, &p1->zp, &p2->zp);
      else
        ZB_line(c->zb, &p1->zp, &p2->zp);
    }
  } else if ((cc1 & cc2) != 0) {
    return;
  } else {
    dx = p2->pc.X - p1->pc.X;
    dy = p2->pc.Y - p1->pc.Y;
    dz = p2->pc.Z - p1->pc.Z;
    dw = p2->pc.W - p1->pc.W;
    x1 = p1->pc.X;
    y1 = p1->pc.Y;
    z1 = p1->pc.Z;
    w1 = p1->pc.W;

    tmin = 0;
    tmax = 1;
    if (ClipLine1(dx + dw, -x1 - w1, &tmin, &tmax) && ClipLine1(-dx + dw, x1 - w1, &tmin, &tmax) &&
        ClipLine1(dy + dw, -y1 - w1, &tmin, &tmax) && ClipLine1(-dy + dw, y1 - w1, &tmin, &tmax) &&
        ClipLine1(dz + dw, -z1 - w1, &tmin, &tmax) && ClipLine1(-dz + dw, z1 - w1, &tmin, &tmax)) {
      interpolate(&q1, p1, p2, tmin);
      interpolate(&q2, p1, p2, tmax);
      gl_transform_to_viewport(c, &q1);
      gl_transform_to_viewport(c, &q2);

      if (c->depth_test)
        ZB_line_z(c->zb, &q1.zp, &q2.zp);
      else
        ZB_line(c->zb, &q1.zp, &q2.zp);
    }
  }
}

/* triangle */

/*
 * Clipping
 */

/* We clip the segment [a,b] against the 6 planes of the normal volume.
 * We compute the point 'c' of intersection and the value of the parameter 't'
 * of the intersection if x=a+t(b-a). 
 */

#define clip_func(name, sign, dir, dir1, dir2) \
  static float name(V4* c, V4* a, V4* b) {     \
    float t, dX, dY, dZ, dW, den;              \
    dX = (b->X - a->X);                        \
    dY = (b->Y - a->Y);                        \
    dZ = (b->Z - a->Z);                        \
    dW = (b->W - a->W);                        \
    den = -(sign d##dir) + dW;                 \
    if (den == 0)                              \
      t = 0;                                   \
    else                                       \
      t = (sign a->dir - a->W) / den;          \
    c->dir1 = a->dir1 + t * d##dir1;           \
    c->dir2 = a->dir2 + t * d##dir2;           \
    c->W = a->W + t * dW;                      \
    c->dir = sign c->W;                        \
    return t;                                  \
  }

clip_func(clip_xmin, -, X, Y, Z)

    clip_func(clip_xmax, +, X, Y, Z)

        clip_func(clip_ymin, -, Y, X, Z)

            clip_func(clip_ymax, +, Y, X, Z)

                clip_func(clip_zmin, -, Z, X, Y)

                    clip_func(clip_zmax, +, Z, X, Y)

                        float (*clip_proc[6])(V4*, V4*, V4*) = {clip_xmin, clip_xmax, clip_ymin,
                                                                clip_ymax, clip_zmin, clip_zmax};

static inline void updateTmp(GLContext* c, GLVertex* q, GLVertex* p0, GLVertex* p1, float t) {
  if (c->current_shade_model == GL_SMOOTH) {
    q->color.v[0] = p0->color.v[0] + (p1->color.v[0] - p0->color.v[0]) * t;
    q->color.v[1] = p0->color.v[1] + (p1->color.v[1] - p0->color.v[1]) * t;
    q->color.v[2] = p0->color.v[2] + (p1->color.v[2] - p0->color.v[2]) * t;
  } else {
    q->color.v[0] = p0->color.v[0];
    q->color.v[1] = p0->color.v[1];
    q->color.v[2] = p0->color.v[2];
  }

  if (c->texture_2d_enabled) {
    q->tex_coord.X = p0->tex_coord.X + (p1->tex_coord.X - p0->tex_coord.X) * t;
    q->tex_coord.Y = p0->tex_coord.Y + (p1->tex_coord.Y - p0->tex_coord.Y) * t;
  }

  q->clip_code = gl_clipcode(q->pc.X, q->pc.Y, q->pc.Z, q->pc.W);
  if (q->clip_code == 0) gl_transform_to_viewport(c, q);
}

static void gl_draw_triangle_clip(GLContext* c, GLVertex* p0, GLVertex* p1, GLVertex* p2,
                                  int clip_bit);

void gl_draw_triangle(GLContext* c, GLVertex* p0, GLVertex* p1, GLVertex* p2) {
  int co, c_and, cc[3], front;
  float norm;

  cc[0] = p0->clip_code;
  cc[1] = p1->clip_code;
  cc[2] = p2->clip_code;

  co = cc[0] | cc[1] | cc[2];

  /* we handle the non clipped case here to go faster */
  if (co == 0) {
    norm = (float)(p1->zp.x - p0->zp.x) * (float)(p2->zp.y - p0->zp.y) -
           (float)(p2->zp.x - p0->zp.x) * (float)(p1->zp.y - p0->zp.y);

    if (norm == 0) return;

    front = norm < 0.0;
    front = front ^ c->current_front_face;

    /* back face culling */
    if (c->cull_face_enabled) {
      /* most used case first */
      if (c->current_cull_face == GL_BACK) {
        if (front == 0) return;
        c->draw_triangle_front(c, p0, p1, p2);
      } else if (c->current_cull_face == GL_FRONT) {
        if (front != 0) return;
        c->draw_triangle_back(c, p0, p1, p2);
      } else {
        return;
      }
    } else {
      /* no culling */
      if (front) {
        c->draw_triangle_front(c, p0, p1, p2);
      } else {
        c->draw_triangle_back(c, p0, p1, p2);
      }
    }
  } else {
    c_and = cc[0] & cc[1] & cc[2];
    if (c_and == 0) {
      gl_draw_triangle_clip(c, p0, p1, p2, 0);
    }
  }
}

static void gl_draw_triangle_clip(GLContext* c, GLVertex* p0, GLVertex* p1, GLVertex* p2,
                                  int clip_bit) {
  int co, c_and, co1, cc[3], edge_flag_tmp, clip_mask;
  GLVertex tmp1, tmp2, *q[3];
  float tt;

  cc[0] = p0->clip_code;
  cc[1] = p1->clip_code;
  cc[2] = p2->clip_code;

  co = cc[0] | cc[1] | cc[2];
  if (co == 0) {
    gl_draw_triangle(c, p0, p1, p2);
  } else {
    c_and = cc[0] & cc[1] & cc[2];
    /* the triangle is completely outside */
    if (c_and != 0) return;

    /* find the next direction to clip */
    while (clip_bit < 6 && (co & (1 << clip_bit)) == 0) {
      clip_bit++;
    }

    /* this test can be true only in case of rounding errors */
    if (clip_bit == 6) {
#if 0
      printf("Error:\n");
      printf("%f %f %f %f\n",p0->pc.X,p0->pc.Y,p0->pc.Z,p0->pc.W);
      printf("%f %f %f %f\n",p1->pc.X,p1->pc.Y,p1->pc.Z,p1->pc.W);
      printf("%f %f %f %f\n",p2->pc.X,p2->pc.Y,p2->pc.Z,p2->pc.W);
#endif
      return;
    }

    clip_mask = 1 << clip_bit;
    co1 = (cc[0] ^ cc[1] ^ cc[2]) & clip_mask;

    if (co1) {
      /* one point outside */

      if (cc[0] & clip_mask) {
        q[0] = p0;
        q[1] = p1;
        q[2] = p2;
      } else if (cc[1] & clip_mask) {
        q[0] = p1;
        q[1] = p2;
        q[2] = p0;
      } else {
        q[0] = p2;
        q[1] = p0;
        q[2] = p1;
      }

      tt = clip_proc[clip_bit](&tmp1.pc, &q[0]->pc, &q[1]->pc);
      updateTmp(c, &tmp1, q[0], q[1], tt);

      tt = clip_proc[clip_bit](&tmp2.pc, &q[0]->pc, &q[2]->pc);
      updateTmp(c, &tmp2, q[0], q[2], tt);

      tmp1.edge_flag = q[0]->edge_flag;
      edge_flag_tmp = q[2]->edge_flag;
      q[2]->edge_flag = 0;
      gl_draw_triangle_clip(c, &tmp1, q[1], q[2], clip_bit + 1);

      tmp2.edge_flag = 1;
      tmp1.edge_flag = 0;
      q[2]->edge_flag = edge_flag_tmp;
      gl_draw_triangle_clip(c, &tmp2, &tmp1, q[2], clip_bit + 1);
    } else {
      /* two points outside */

      if ((cc[0] & clip_mask) == 0) {
        q[0] = p0;
        q[1] = p1;
        q[2] = p2;
      } else if ((cc[1] & clip_mask) == 0) {
        q[0] = p1;
        q[1] = p2;
        q[2] = p0;
      } else {
        q[0] = p2;
        q[1] = p0;
        q[2] = p1;
      }

      tt = clip_proc[clip_bit](&tmp1.pc, &q[0]->pc, &q[1]->pc);
      updateTmp(c, &tmp1, q[0], q[1], tt);

      tt = clip_proc[clip_bit](&tmp2.pc, &q[0]->pc, &q[2]->pc);
      updateTmp(c, &tmp2, q[0], q[2], tt);

      tmp1.edge_flag = 1;
      tmp2.edge_flag = q[2]->edge_flag;
      gl_draw_triangle_clip(c, q[0], &tmp1, &tmp2, clip_bit + 1);
    }
  }
}

void gl_draw_triangle_select(GLContext* c, GLVertex* p0, GLVertex* p1, GLVertex* p2) {
  gl_add_select1(c, p0->zp.z, p1->zp.z, p2->zp.z);
}

#ifdef PROFILE
int count_triangles, count_triangles_textured, count_pixels;
#endif

void gl_draw_triangle_fill(GLContext* c, GLVertex* p0, GLVertex* p1, GLVertex* p2) {
#ifdef PROFILE
  {
    int norm;
    assert(p0->zp.x >= 0 && p0->zp.x < c->zb->xsize);
    assert(p0->zp.y >= 0 && p0->zp.y < c->zb->ysize);
    assert(p1->zp.x >= 0 && p1->zp.x < c->zb->xsize);
    assert(p1->zp.y >= 0 && p1->zp.y < c->zb->ysize);
    assert(p2->zp.x >= 0 && p2->zp.x < c->zb->xsize);
    assert(p2->zp.y >= 0 && p2->zp.y < c->zb->ysize);

    norm = (p1->zp.x - p0->zp.x) * (p2->zp.y - p0->zp.y) -
           (p2->zp.x - p0->zp.x) * (p1->zp.y - p0->zp.y);
    count_pixels += abs(norm) / 2;
    count_triangles++;
  }
#endif

  if (c->texture_2d_enabled) {
#ifdef PROFILE
    count_triangles_textured++;
#endif
    ZB_setTexture(c->zb, c->current_texture->images[0].pixmap);
    ZB_fillTriangleMappingPerspective(c->zb, &p0->zp, &p1->zp, &p2->zp);
  } else if (c->current_shade_model == GL_SMOOTH) {
    ZB_fillTriangleSmooth(c->zb, &p0->zp, &p1->zp, &p2->zp);
  } else {
    ZB_fillTriangleFlat(c->zb, &p0->zp, &p1->zp, &p2->zp);
  }
}

/* Render a clipped triangle in line mode */

void gl_draw_triangle_line(GLContext* c, GLVertex* p0, GLVertex* p1, GLVertex* p2) {
  if (c->depth_test) {
    if (p0->edge_flag) ZB_line_z(c->zb, &p0->zp, &p1->zp);
    if (p1->edge_flag) ZB_line_z(c->zb, &p1->zp, &p2->zp);
    if (p2->edge_flag) ZB_line_z(c->zb, &p2->zp, &p0->zp);
  } else {
    if (p0->edge_flag) ZB_line(c->zb, &p0->zp, &p1->zp);
    if (p1->edge_flag) ZB_line(c->zb, &p1->zp, &p2->zp);
    if (p2->edge_flag) ZB_line(c->zb, &p2->zp, &p0->zp);
  }
}

/* Render a clipped triangle in point mode */
void gl_draw_triangle_point(GLContext* c, GLVertex* p0, GLVertex* p1, GLVertex* p2) {
  if (p0->edge_flag) ZB_plot(c->zb, &p0->zp);
  if (p1->edge_flag) ZB_plot(c->zb, &p1->zp);
  if (p2->edge_flag) ZB_plot(c->zb, &p2->zp);
}
